Sinclair 128K problem

JLPedro

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Here's one for the Speccy techs out here:

Got a Sinclair 128K Heat-sink UK version with the following problem, all works 100% except no AY sound output, nothing, plays 48k sound and i can ear the key strokes with speakers connected to the EAR socket (TV output sound is only noise on both beeper or AY sound, image is fine).
I'm using an +2 psu (9v 2,1 amps) and it reads perfect values. Other things i checked were the IC 7805cs and it reads 5,05v and 11,50v (strange as the psu outputs 12v and on the ic only gets 11,50v...), also checked the AY-3-812A 5v pin and it reads 5,02v (+5v pin 3 and GND pin 6).

Any ideas??
 

JLPedro

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Is there a way to really be sure is the Ay chip at fault, as it is very difficult for me do desolder that kind of ic (only have a basic solder sucker).
And can I use the AY chip from a +2 Grey spectrum?
 

amigaman2000

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Hi JLPedro

First of all, TV output sound is only noise because UK PAL and European PAL are slight different in modulation sound. Second, I agree with rkauer, try to replace the audio chip, is the same as you can found in the Speccy +2 grey model, and in other home computers.

Regards
 

JLPedro

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Will do that then, going to post an wanted for a AY-3-8912A chip.

Thanks for all the help (y).
 

rkauer

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Remember to use a socket for the replacement instead direct soldering.

Oh, socket strips are perfect for this.
 

JLPedro

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Litle update on this, conecting the mic socket to my creative speaker amplifier i get a loud amp sound and if listening carefuly you can ear the AY sound of the game very low.

So this means the AY chip is ok and the problem is or the socket or some component between the ay chip and the mic socket.
Is the mic socket amplified on the 128K+ ?
 

UberFreak

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AFAIK, on all original Spectrums, 'ear' plug is output, 'mic' is input.
So you need to connect to 'ear'.

In any case, its just a standard line-level output.
 

zaxon

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In ay chip pin 1,4,5 is audio output, try connect speaker to this point.and ground. If sound back something is wrong beetwen chip and mic output , propably capacitor is broken.
 

zaxon

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check again, we talking about ay 3-8912, pin,1,4,5 is 3 channel audio output, in spectrum connected together, pin 6 is 5 volt power supply


Sorry, pin 3 is 5 volt power supply, pin 6 is GND, anyway just try connect pin,1or 4,or 5 and ground to speakers, also not all game use AY chip.
 

JLPedro

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Sound now playing 100%!!! :bowdown: Now enjoing the retro play of true Sinclair 128K+ and DivIDE awsomeness!!!

Bad audio socket solder join and bad "new" 7805 IC :blink: (replaced for another new one :p)


AFAIK, on all original Spectrums, 'ear' plug is output, 'mic' is input.
So you need to connect to 'ear'.

In any case, its just a standard line-level output.

Nope, "MIC" is output and "EAR" input.
 

John58

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That’s great news Pedro, glad it turned out to be something simple in the end. Strange that you could hear the beep sounds through the bad solder joint, then again I read some were that the beep volume is the same as all 3 ay channels playing together so will be a lot louder.


John
 

JLPedro

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That’s great news Pedro, glad it turned out to be something simple in the end. Strange that you could hear the beep sounds through the bad solder joint, then again I read some were that the beep volume is the same as all 3 ay channels playing together so will be a lot louder.


John

Indeed, but socket was not the main issue, the 7805 that i used to replace the original was at fault also so probably afecting more the AY chip.
Beeper sound is still a bit louder than AY as you pointed (in a scale of 10 i'd give 10 on the beeper and 8 on the AY for loudness), really don't know if normal or not but both give 100% clear sound now.

@zaxon

Nice videos, expecially the Atari 65xe ones as something extraordinary happened yesterday to a good friend of mine here in Portugal!!

He pulled from the garbage a near MINT Atari 130XE computer on his way back home from shopping!!!!!
 

zaxon

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Hyhy,it is Christmas time so miracles happens,LOL. My friend in France found Atari Falcon in orginal box !!!
 
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